ELI5: Explain Like I'm 5

Sumset

Alright kiddo, let me try to explain sumset to you in a way that you'll understand.

Imagine you have a bag of toys. Each toy has a number on it. Now, say you want to know all the possible ways you can add two toys together to get a certain number. For example, you want to know all the ways you can add two toys to get 5.

Let's see, you could take the toy with the number 2 and combine it with the toy with the number 3. Or you could take the toy with the number 1 and combine it with the toy with the number 4. Those are two possible ways to get the sum of 5.

Now imagine doing this for all possible sums you could make with two toys in the bag. This is what we call the sumset - it's the set that contains all the possible sums you can make by adding two toys from the original set.

And that's it! Sumset is just a fancy way of saying "all the possible ways to add two numbers together".